Block signaling system for railroads



l t 0u 2. 5. Qu .2 e A e h S sm D A O R u L Am TR1 EMM ...n.MJ mm? SYW8.5M EG.d N WIe Ln BMF .F.u.. OS K C 0 L B July 4, 1944.

July 4, 1944.` o. E. WEBSTER ET A... 2,352,986

BLOCK SIGNALING SYSTEM FOR RAILROADS Filed May '7, 1941 14 Sheets-Sheet2 @TJ u B Coley 952ML@ N.4 d 5 n Y .ENE T R @Mdm V WIEDQMA e R w v Y.0.8 T

EEEEEEE fill? I IL E E uucepm EAE www1?. .@.Hrm

July 4, 1944- l lo. E. WEBSTER ET AL 2,352,986

BLOCK SIGNALNG SYSTEM FOR RAILOADS Fned May 7, 1941 14 sheets-sheet 5m6@ N. n@ mm n A mm. m MDN 20m. s T A Nm. E u O 8m@ w V.T u N 5 A I .Wwn ma ILS m L @mmh r. @m NIH SENER@ mm @ma @N QN 2S 2.3m@ o@ .lr sin@.12m

July 4 1944' o. B. WEBSTER ETAL BLOCK SIGNALNG SYSTEM FOR RAILROADSFiled May '7. 1941 14 sheets-sheet 4'- SVIJB@ INVENToRs OlWe bster' andNBCoIey MM. @im THem ATTORNEY PMM vm25 NE July 4,

Filed May 7,- 1941 FIGzgA.-

14 Sheets-Sheet 5 THEIR ATTORNEY July 4, 1944. o. B. wEBs-rl-:RA ETA..

BLOCK` SIGNALING `SYSTEM FOR RAILROADS Filed May '7, 1941 14Sheets-Sheet 6 TH EIR ATTORNEY July 4,1944 o. B. WEBSTER E-r AL2,352,986

BLOCK SIGNALIING SYSTEM FOR RILROADS Filed May'., .1941 14 Sheets-Sheet'l'4 y,

THEIR ATTORNEY July 4, 1944- o. B. WEBSTER E-rAL` 2,352,986

yBLOCK SIGNALING SYSTEM FOR RILROADS l File'd May 7, 1941 14Sheets-Sheet 9 T BQA- A. I

THEIR ATTORNY f JT- lNVENT-(SRS OBVVebs r' and N BColey .BY M

July 4 1944 o. B; WEBSTER ET AL 2,352,986

BLOCK SIGNALING SYSTEM FOR RALROADS Filea May 7, 1941 14 SheeLS-Sheet 10THEIR ATToRN'EY v f July 4, 1944. o. B. WEBSTER ETAL l BLOCK SIGNALINGSYSTEM FOR RAILROADS WIIIIII ,Ud J u. a .f @hmm m mi @NR Mar @.2 E @S M.w. NMR.. mu. 5N. m ahw mkwm W n B lmm mV TINE. M F E Tl M www, ab W. F.w 1 .4 9 1 7. v.. a M ,d .1 F

11111 4, 1944- o. B. WEBSTER ETAL 211,352,986

BLOCK SIGNALING SYSTEM FOR RAILRODS Filed May y'7, 1941 *'14Sheets-Sheet 12 57 FIGA. vn-@@@La l 1' I s Ml l l/T? l/TQA 7HD l 487 1 II @1:29 NDP@ #L16 well v I l Y H .R 717 1w l 47 i sa f T6 @HD l 5HD BHDPl 415 w 5a?! I Lh l '495| L I l INVENTOR QYBWeb ramd NBColey THEIRATTORNEY July 4 1944- o. B. WEBSTER ETAL v2,352,986

BLOCK SIGNALING SYSTEM FOR RAILRODS Qwebser and NBColey TH Em ATTORNEY fJuly` 4, 1944.,

O. B. WEBSTER ETAL BLOCK SIGNALING SY-STEM FOR AILROADS Filed May 7,1941 7 14 sheets-sheet 14 GBM/ebs @rand NColy BY THEIR ATroRNY PatentedJuly 4, 1944 BLOCK SIGNALI NG SYSTEM Fort RAILROADS` Osborne B. Websterand Nelson-B. Ooley, Rochester, N. Y., assignors to General RailwaySignal Company, Rochester, N. Y.

Application Mayl 7, 1941, Snerial No. 392,298 36 Claims. .;;1(Cl.246-33) The present inventionrelates to railway signaling for singletrack railroads and more particularly to signaling of theabsolute-permissiveblock type.

Railway signaling of the absolutepermissiveblock type employing trackcircuits and one line circuit for each direction of trailic, the twoline circuits for'opposite directions of traffic employing a common wiresothat a total of three wires only were used, is .well known to thoseskilled in the art of single track signaling. Theseabsolutepermissive-block signaling systems earlier usedandremployingthree line wires however required at least two intermediatesignals, which were s single .track railway signaling system o f the abfsolute-permissive-block type in which less than double or even singlelbraking distance between a pair of staggered intermediate signals may beemployedA and at the same time afford absolute signaling protectionagainst the movement of 'trains in opposite `vdirections through the'signal track section and to provide the facility of permissivesignaling protection, that is, provide Vat least one danger 'signalfollowed by a caution signal to the rear of a train'moving through thesingle track section of vthe railway system so vthat a second train mayfollow the iirst train with adequate lsignaling between the two trains.To accomplish these 'ends it is proposed in accordance with the presentinventionfto provide a caution tumble-down signaling function, so tospeak, whena train is a considerable distance to the rear of theentran'ceto a single track section and to provide the usual dangertumble-down signaling function upon the entrance of a train into f.

thev single track section. In order to accomplish these results one'ofthe features provided inaccordance with the present invention resides inthe provision of a directional stick relay for each intermediate signalina single track section, and for eachentering signal governingentranceA of traflic into the main track or 'side track of the passingsiding, which directional stick relaywhen once picked up is held upuntil the associatedsignal is'controlled to, itsclear indication :v

condition.

lpresence of this east-bound train;

, y Another object of the present invention-,resides in the provision ofcircuits and devices for causing the intermediate signals in twoadjacent single track sections to indicate caution in response to thejointV action of two opposing trains entering the distant ends of suchtwo single track sections connected by a passing siding. In one form ofthe present invention separate home and distant relays controlled overindividual line circuits, instead vof polar-neutral devices eachcontrolled over a polar line circuit, are employed.

Other objects, purposes, and characteristicfeatures of the'presentinvention will, to a large extent, be pointed out in detail inthe'following description and Will in part be obviousfrom theaccompanying drawings, in which:y n o Figs. 1A, 1B, 1C and 1D illustratein detail the circuits of an absolute-permissive-block signaling` systemembodying-the present invention, certainportions of this circuit diagramconstituting modifications for other portions thereof; l

Figs. 2A to 13A and 2B to 13B villustrate schematically the railwaysystem shown'inFigs. 1A- 1B with an east-bound train assuming' variouspositions on this system and in which the signals assume indicatingconditions dependent onthe Figs. 14A to 25A and 14B to 25Billus'tratethe same railway track layout as illustrated in Figs. 2A-l3B butillustrate signal indicationsin'accordance with the position assumed byawes't'- bound train at various instances during its movement over therailway system illustrated;

f Figs. 26A to 37A and Figs. v26B to 37B illustrate the same portion ofthe railway system as illustrated in Figs. 2A-13B and 14A-25B, exceptfor the addition of a portion of another passing siding and anadditional single track section including intermediate signals S0, Sland S2, with the signals giving various signal indications dependent onthe presence of an east-bound train and a west-bound train at variouspoints along the track so chosen that these two trains mak al meet atthe passing sidingrA; Fig. .38 shows a modified signaling systememploying polar type search-light signals; o

Fig. 39 shows a modified system employing two neutral circuits eachincluding a neutral relay for each polar circuit including apolar-neutral relay employed in Figs v1A--1D.

Fig. 40 shows a modied-circuit construction for-the intermediatesignals. Y Figs. 41A to 52B show the signal aspects under Variousytrafcconditions when the Acircuit. construction of Fig.40. is employed; and

Fig. 53 shows a modied control for the intermediate signals to providean overlap control for the caution tumble down feature.

STRUCTURE Referring to Figs. 1A to 1D, inclusive, it will be seen thatthe passing sidings A and C have been illustrated connected by a singletrack section B and that an additional single track section D has beenillustrated to the right of the passing siding C. This -railwaysignaling system shown in Figs. lA-lD includes track rails `9 divided byg insulating joints l0 into track sections which are track circuited bytrack circuits including the usual track battery B and track relay T. In

order to distinguish these varioustrack batteries and track relays fromeach other each of these reference characters T and B is followed by asuix number corresponding to the number of the track circuit, each trackcircuit being numbered in accordance with the signal that it mostdirectly controls.

Each stretch of track extending from one signal to another governingtrafc in the same direction is provided with a common wire C, an

east-bound control line wire E, and a west-bound control line wire W.Each of the signals has been designated S with a sufx number todistinguish these signals from each other. These vsignals may be of anysuitable construction, as for instance, semaphore signals, movablespectacle search-light signals, or multi-unit light signals, and forconvenience multi-unit light signals having green (clear), yellow(caution), land red (danger) signal units designated G, Y and R,respectively, have been illustrated for the systems shown in Figs. lA-lDand Fig. 39, searchlight type signals having been shown in Fig. 38. 4Forthis reason the polar-neutral home-distant relay for each signal of Fig.1 may be consid- .ered to be the electro-responsive means ofthe signalin the same Way as though a search-light similar manner the head-blocksignal at the west end of the passing siding C has been designated S9and its associated entering signal has been designated SIB, whereas thehead-block signal at the east end of the passing siding C has beendesignated SI2 and its associated entering signal has been designated SIReferring now to the single track section B v(see Fig. 1B of thedrawings), the intermediate west-bound and east-bound signals thereofhave been designated S1 and S8, respectively, where- -as thecorresponding intermediate signals for the single track section D (seeFig. 1D) have been designated S|3 and SI4, respectively. It is thusapparent that all of the east-bound signals have been designated S witha sufx of even number, whereas the west-bound signals have beendesignated S followed by an odd numbered suiiix.

Referring now to the signal location having a pair of opposite signalsS5 and S located at the east end of the passing siding A (see Fig. lA),this signal location includes hole-distant polarneutral relays EHD andBHD provided with repeater relays EHDP and GHDP, respectively,

which home-distant relays each directly control the associated signalhaving a suffix number corresponding to the prefix number assigned tosuch relay. The manner in which these home-distant relays HD and theirrepeater relays HDP control their respective signals is indicated indetail for the signal S8 (see Fig. 1B of the drawings). The enteringsignal S5 has' associated therewith a directional stick relay 5S andsimilarly the head-block signal SE has associated therewith adirectional stick relay ES. The switch at the east end of the passingsiding A has been designated Sw56 and it has associated therewith a pushbutton PB5-6. This push button controls a push button relay PBR5--6 anda push button repeater relay PBRPS-(. The functions performed by thispush button and its associated push button relays will be morespecifically pointed out hereinafter. These track relays T, home-distantrelays HD, home-distant repeater relays HDP, directional stick relays S,push button relays PBR, and push button repeater relays PBRP at otherlocations on the railway signaling system have been assigned likereference characters having distinctive prefixes or suffixes, as thecase may be.

In order to obtain a more clear understanding of the circuits employedthe circuits for the various relays associated with signals S5, S6 andSB will be described in detail and thereafter like contacts of othercircuits will be assigned corresponding reference characters havingdistinctive exponents. Referring to Figs. 1A and 1B ofthe drawings thehome-distant relay 6HD is under normal clear traic conditions energizedthrough the following circuit: beginning at the terminal (-1-) of asuitable source of current, polar contact I58 of the relay BHD assumingits normal right-hand position, front contact |58 of the home-distantrepeater relay BHDP, front contact |'|6A of the track relay TSA, linewire E6, front contact |86 of the track relay T6, winding of thehome-distant relay BHD through the common return Wire C, through frontcontact I98 of the home-distant repeater relay 8HDP, through contact2|)8 of the home-distant relay BHD assuming its normal right-handposition, to the other terminal of the same source of current. There areother energizing circuits for the homedistant relay SHD which includecontacts H8, |28, I3B and |118 of the directional stick relay 8S, butthese additional circuits Will be discussed in connection with theoperation of the system hereinafter. The energizing circuit for thehomedistant repeater relay BHDP includes a front contact 226 of thehome-distant relay BHD.

The home-distant relay 5HD is under normal clear traflic conditionsenergized through a circuit which may be traced as follows: beginning atthe terminal of a suitable source of current, front contact 211|3 of thehome-distant repeater relay 3HDP, front contact 253 of the track relayT3, front contact 2B4 of the track relay T4, front contact 215 of thetrack relay T5, winding of the home-distant relay 5I-ID, through frontcontact 283 of the home-distant repeater relay 3HDP to the otherterminal of the same source of current. When there is a west-bound trainoccupying the track section directly ahead of the signal S3 thehome-distant relay BHD is energized through a similar circuit, includingthe front contact 233 of the directional stick relay 3S instead of thefront contact 25.3 of the track relay T3. The home-distantrepeater'relaySHDP is energized-through a circuit including a front Contact 295 of thehome-distant relay 5HD.

The directionalstick relay 5S is provided with av pickLup circuit whichmay be traced as follows beginning at" the terminal of a suitable sourceof current, track switch repeating contacts |'Sw5-6, backl Contact 305of the track relay T6, back contact 3 l5 of the track relay T5, frontcontact 325 of thehome-distant repeater relay SHDP through the Windingof the directional stick relay 5S and to the otherterminal of the samesource. This stick relay 5S vis also provided with three stickcircuitsasfollows: (l) a stick circuit including'switch repeating contactISw5-6, stick contact 335 of the stick relay 5S and back contact 325 ofthe home-distant repeater relay SHDP, (2) a 'stick circuit including theswitch repeating contact ISw5-6,the stick contact 335 ofthe relay 5S and'the back contact 345 of the home-distant relay 5HD, and (3) a stickcircuit including the sameswitch repeating contact and stick contact andalso includingthe front contact 385 and the polar contact395 in'itsleft-hand caution position of the home-'distant relay 5HD. Similarly,the

directional stick relay 6S is provided with a pickup circuit including.the switch repeating contact -ISw5`-l, .back contacts 365 and 3l5 ofthe track relays T8 'and,T5, respectively, and front contact 35 of thehome-distant repeaterk relay BHDP;

andthe two stick circuits for this directional stick relay SS include:(l) the switch repeating contact |Sw5-6, stick contact 366 of thedirectional stick relay 6 S, and backfcontact 355 of the homef distantrepeater relay BHDP, and (2) switch rebeating contact ISw5-6, stickcontact 366 of the directional stick relay, GS, and loack contact 316c-f the home-distant relay GHD. A y Under normal clear trainolconditions the home-distant relay BHD (see Fig. 1B) isl energizedthrough a circuit which may be traced as follows: beginning at'theterminal (-1-) of a suitable source of current, front contact lill0 ofthe kpole changer relay IDPC, front contact 429-10 of the push buttonrelay PERB-I0, front contact 43.9.*10 of the push. button Nrepeaterrelay PBRPS-QID, 'iront contact 449 of the track relay T9, wireE8,`,'front contact 459A, of the track relay T9A, back contact t67 ofthe directional stick relay 1S, front contact 4TI of the track relay T1,wire E8, front contact 488 of the track relay T8, winding of .thehome-distant relay 8HD, to common' return Wire `C, land through frontcontact 4915 of the pole changer relay HIPC, to the other terminal ofthe same source of current. Upon movement of the pole changer relay IUPCto its retracted position the' energizing circuit for this home-distantrelay BHD is exactly the same as just traced, except that the polarityof energization of the circuit has vbeen reversed. This pole changerrelay I8PC (see Fig. 1C) is under normal clear traffic conditions of thesignaling systemy energized by a circuit beginning. at the source polarcontact 5010 of the home-distant relay IUI-ID, assuming its right-handclear position, front contact 5|1 ofi the home-distant repeater relayIBHDP, through the winding of the pole-changer relay IUPC and to theterminal of the same source. "There are three addi'f tional circuits forthe pole-changer relay; v(l) through-'frontcontacts 5210 and 539 ofrelays T IU and SHD, respectively, and back contact 5l1 of relay IOHDP;(2) through front contacts 5215 and 539 of relays -Tl0 and 9HDrespectively, through back contact 541,o of directional stick relayyIOS,

throughl contact 5815 of relay` IUHD assuming its 'wie the remainingdetectortrack circuits.

left-hand 'caution position and. front contact 5|10 of`relay. IDHDP;Aand (3) acircuit through front contact VA541 of. directional stickrelayV I 0S, through Vpolar contact 501 assuming its left-hand positionand front-'contact 5I1 of relay' I lll-IDP.

These circuits will be more fully discussed hereinafter in connectionwith the operation of the system.-

It is readily seen that the control circuits for stick relays 3S and 4Sare respectively identical to the control circuits for the stick relaysBS and 5S and since the control circuits for these latter relays havealready beenftra'ced the control circuits for the formerrelays need notbe traced. It is also readily seen thatthe control circuits for stickrelays v'ES and 8S are identical andfurther are similar to the ycontrolcircuits for stick relays 4S and 5S in thatlone stick circuit for eachof stick relays 4S, 5S, 1S and 8S includes a caution contact of itsassociated :home relay. For thisreason the pick-upgcircuit and lstickcircuits for the directional Ystick relay 8S will be specificallydescribed This directional stick re-V lay 8S is. provided with a pick-upcircuitrinclud.- ing. back contacts 568 and5'l6A of the track re'` laysT8 and TGA, respectively, and front Contact 588 of the home-distantrepeater ,relay BHDP. This directional stick relay includes three stickcircuits which may be traced as follows: (l) the stick circuit includingthe stick contact 6115 of the stick relay 8S, and the back contact 583of the home-distant repeaterrelay I-IDP, (2) the stick circuitincludingA the stick contact 655 of the stick relay 8S and the backcontact 615 of the track relay T8, and (3) the stick circuit includingthe stickcontact 605 of the stick relay 8S,.the polar contact 628 of thehome-,distant relay BHD assuming its left-hand caution position, and thefront neutral contact 638 of this same home-distant relay 8HD. Thecircuitsfor the directional stick relays associated with the remainingintere mediate signals are identicaland for thisl reason like contactsin their pick-up and stick circuits havebeen assigned like referencecharacters with distinctive exponents. l Y

AThe push button relay FBR56 (Fig. 1A) is normally energized throughacircuit including in series the switch repeating contact lSw-G and thenormally closed contact of the push button PB5-6. The push buttonrepeater relay PBRP5-6 is normally energized through lthe front contact655-5 of the push button relay PBR5--6.` The track repeater relay TPM iscontrolled cthrough front cont-act 69M of the track relay Tl4, so thatthese relays TI4 and T1514 pick up yand drop in substantial synchronismlIt will' be observed that the detector track circuits associated withtrack switches Sw3-4, SwE-B, Sw9-l8 and Sw! I-l2 extend substantiallyhalf way through the main track of the passingsidings (see Figs. 1A and1C). In order to prevent the clearing of an entering signal to a passingsiding when one of these track switches is operated, each of thesedetector track circuits is provided with means to short-circuit thetrack rails thereof when the track switch is open. As illustrated thisis accomplished by the track switch repeating contact 2Sw5--6 for thedetector track circuit at the east end of the passing siding A, vsimilarcontacts being provided for Not only will an open track switch put tostop the entering signal .(such as signal S5)V at that end of thepassing siding, but it,will also put the entering signal (suchv assignal. S4) at Vthe Opposite end,

hereinafter the opening oa tracleswitcliL will also4 cause a caution'tumble` down of-v signals through-.the adjacent single track .stretch tooccur, For reasons obvious from the drawings and pointed out hereinafterthe signal (such as signalv Sl). next to the rear of an enteringsignal(such as signal S5) will at times be allowedI to clear even though suchentering signal is then at stop.

. vAs heretofore pointed out certain portions of the system'illustratedin Figs. iA-lD constitute modifications of other and similar portionsAof theisame system. For instance, instead .ot using what is known as acut section, meaning that a. block is divided by insulating joints intotwo Sections, each sectionof which is separately track .circuited, suchas is employed between the signals S1 and S8 (see Fig. 1B) it may bedesirable to employ a single track circuit with the track'relay repeatedat the opposite end of thesection through the medium of a track repeaterrelay.

Such an arrangement is shown between the signals SIB and Sill in Fig. lDof the drawings where the relay TPM repeats the track relay Ti Referringparticularly to Figs. 1A and 1B of the drawings, attention isparticularly directed tothe energizing circuit for the home-'distantrelay lill), and particularly to the contactswliicli control theapplication of energy to the west end of this control circuit. It will'be noted that under normal conditions this line circuit is enerm gizedthrough iront pole-changer contacts H5 and 495 ci the pole-changer relayEPG. -A'lso under such normal conditions this relay EPC is energizedover polar contact 55 of: the lrelay EHD assuming its right-handposition and through iront contact 545 ci the home-distant repeaterrela-y Fil-IDP. It will 'also be seen that when the polar contact 505 ofrelay Eli-ID is in its caution or left-hand position that energizationof the pole-changer relay 5PCt-is/ then dependent on the position ofcontacts `525,536 and 545 of relays T5, EHD and 5S respectively. It willalso be noted that pole changing of this circuit for home-distant relay'II-ID may be accomplished by these latter contacts l525 and 536 eventhough the home-distant repeater relay SHDP is deenergized (its backcontact 5 t5 closed). In other words, each of the contacts 545,525, 536and 545 at times cause pole changing of the line circuit for relay TED.It is also ofv interest and of considerable importance thatdeenergization of the home-distant relay EHD'and its repeater relay FIDPwill not cause poley changing of the energizing circuit for thehome-distant relay lHD so long as the track relay T5 `and thehome-distant relay EHD are in their energized positions. In other words;if the signal is put to stop by reason of the approach of an eastboundtrain in the single-track section to the leit of the passing siding Athis fact willnot cause the signal S1 to change from a clear to acaution indication as is usually the case. `.For reasons pointed outhereinafter this feature of applicants system is perfectly safe becausesuitable approach control is provided to changethe signal S1 from aclear signal to a caution. signal if. .the signal S5 is at stop when awest-bound train approaches the signal Si and inf'so doing will by theusual dangertumble-down vfunction droprelay fHD and openffrontcontactf'.

ac-asse OPERATION` on THE SYSTEM The' operation of the system willbedescribed under' three sub-headings oi East-bound train movement, a,West-bound train movement, and Two trains making a meet.

Theoperation of the signaling system illustrated inv Figs. lA to 1D,inclusive, will be discussedv by making references to Figs. 2A 13B;Figs. 14A-25B, and' Figs. 2SA-37B of thel drawings, It may be pointedout `that if the sheet of the drawingsy containing Figs. 2A'13A,Y andthe sheet of the'drawings containing Figs. 2B'13B are laid side by side'they will illustrate the sigmaling' system shown in Figs. lAflDrepeated twelve times, in each drawing of which the train or vehicle VIassumes aldifferent position on the railway system than in the precedingdrawing. In la similar'manner thesheets of the drawings containing Figs.14A-25A and Figs. 14E-25B should alsorbe laid side by side, as is alsotrue of the sheets o1" the drawings which contain Figs. 2SA-37A, andFigs. 2GB-37B.

Referring now to Figs..2A and 2B of the drawings'it will be seen thatarrows are sho-wn pointingto the right, that is, toward the east, abovethe track diagram, and that arrows pointing to the left or west areshown below the track diagram. Each of these arrows is symbolic of aline` feeding energy inthe direction indicated by suchl arrow and isprovided with a plus (-1-) sign, a minus sign, or a zero (tl) sign orsymbol at the tail-end of the arrow. This conplied to the line circuitat one signal for con- V' trolling the next signal in the rear, and thesymbols (-1-), orV (0) shown near the middle, of this arrow shows thenature of the control that is'actually transmitted. Forinstance,.referring to the arrow shown directly below the vehicle Vl inFig. 2A of the drawings, it is apparent that (-i) energy has beenapplied to the control circuit extending. from the signal S4, to thesignal next in the rear. thereof, but that this control energy has beencut oi bythe opening of a yfront contact of the track relay due to thepresencel of the train in this section. Referring now to Figs. 9A and 9Bof. the drawings, it will be seen that energy has been applied to thelinecircuit extending from the signal S5 to the signal Sl next in therear thereof,` as shown by the plus applied to the tail-end of the arrowconnecting these signals, but that this energy cannot flow as ismanifested by the symbol zero (El) shown near the middle of this arrow,even though there is no train in this section. The current in thepresent instance is not permitted to flow through the control, circuitextending to the signal Sl because the control circuit is open at theback contact 4 68 of the directional stick relay 8S, `becausethe'vehicle VI has just passed the signalk S81 inan eastwardly directionand has pickedup this relay 8S (see Figs. 9A and 1B ofthe drawings) Inother words, each of the arrows shown in Figs. 2A and 37B of thedrawings conventionally represents a line circuit shown'scmewherein/Figs. 1A to, 1D of the drawings,` and the plus minus or zero (0)signs illustrated at the tail end vof such arrow shows'the nature of thecontrol. applied tothe line circuit, and theplus minus or zerof) symbolnear. themiddle of.V such arrow indicates the actual current, if any,that isiflowinginjthis line circuit. Also,` theletters G, Y or R appliedto each of the signals shownv in Figs. 2A

'to 3713,' inclusive, signies the indication given by such signal underthe traffic conditions then existing.

East-bound train movement Referring to Figs. 2A to 13B, inclusive, itwill be seen that the east-bound train or railway vehicle Vlfhas beenshown at various locations along the track to signify successive.positions of this train during its progress-in an easterly directionover the signaling systemk illustrated in'Figs. 1A to 1D, inclusive.With the railway vehicle VI located as illustrated in Fig. 2A the signalS3 assumes the stop position and the signal S assumes the cautionposition. Reg ferring to Fig 1A it will be seen that the presence of thetrain on the track circuit ,containing .the track battery B3A will.cause deenergizaticn of the home-distant relay SHD (see control circuitfor relay BHD, Fig. 1C), thereby putting the signal S3 to stop becausethe opening of the front contact 293 of home-distant relay BHDdeenergizes the repeater relay 3HDP, thereby opening the front contact103 included in series inthe energizing circuit for the green lamp ofthe signal S3, and `causing the back contact 'm3 to close an energizingcircuit for the red lamp of this'signal S3, the polar contact 'H3 of thehomedistant relay 3HE remaining in its right-hand position. Also,dropping of the home-distant repeater relay 3I-IDP by the dropping of'its pole changer contacts 243 and 283 causes the hornedistant relay SHDto be energized by current of reverse polarity, thereby operating thepolar contact H5 to the reverse position to close the energizing circuitfor the cautionor yellow lampY of the signal S5 and opening of thecircuit for the green o rclear lampG of `this signal S5. ,The nextopposing signal in advance of the train Vl therefore` gives ,a dangerindication, whereas the second'opposing signal S5 in advance of thetrain gives a caution indication as diagr-ammettically illustrated bythe letters R and Y, on the signals S3 andr S5, respectively, of Fig. 2Aof the drawings. e l Let us now assume that the railway vvehicle VI inquestion advances to theposition illustrated in Fig. `3A ofthe drawingsto thereby cause deenergization of thejtrackrelay T3 (see Fig. 1A),Dropping of the track relay T3, among other things, f causes the-openingof its front contact 253],inc1`uded in series in the energizing circuitfor I the home-distant relay 5HD, thereby deenergizing this relay 5HD.Dropping of the relay 5HD places the signal .S5 in its stop conditionasshown by the letter "R in Fig. 3A,

and by the opening. of its front contact 295 deenergizes thehome-,distant repeater relay 5HDP. The droppingv ofzthis repeater relaySHDP causes dropping of its contact 5|5. Since, however, the contacts525 and 536.0f relays T5 zand EI-ID, respectively, 'are now .in theirnormal raised position noA pole changing ofthe energizing circuit forthe home-'distant relay. 'II-ID takes place and the signal S1 remains inits clear indicating condition. The conditions of these various linecircuits under. the two ,traffic conditions is conventionally shown bythe corresponding arrows in Figs. 3A and 3B of the drawings.

Referring againv to Fig.. 3A of the drawings, it will be seen that therailwayvehicle VI has two Opposing stop sign-als S3 and S5 directlyahead F of the train, and has a clear signal S1 to the rear of thesignal S5 at stop. These signals are, however, opposing signals and donot in any way restrict the" movement of the vehicle Vl. Even thoughthere is a clear signal ST directly inthe rear of the stop signal 'S5this does not mean that there is inadequate safety, because if a westbound train were to enter the single track stretch B the signal S1 wouldbe operated to the ca ution position for the same reason that signal S2(Fig. 29A) is operated to caution by the entrancelv of west bound train`into vsingle track stretch B (Fig. 29B) as more particularly pointed outhereinafter. i

Let us now assume that the' trainVl accepts and vpasses the clear signalS4 and assumes the position illustrated in Fig. 4A of the drawings. Thisdoes not affect any ofthe opposing signals in advance of the train, butit does change the signal S4 from a clearsgnal to a stop signal, as isevident from the letters G and R appearing on these signals in Figs. 3Aand 4A', respectively. The movement.l of' this train "VI Hby the signalS4, however, controls signals inthe rear thereof, in part by theenergization of the directional stick relay 4S. For this reasonattention is directed to FigglA of the drawings from-which it isapparent that as the front end of train Vl under consideration passes.the signal S4 it will hold both ofthe track relays T3 and T4`in theirdeene'rgiz'ed position, and'with these track relays T3 and T4 in theirretracted position, and with the home-distant repeater relay 4HDP notyet havin-g responded to the dropping of the home-distant relay 4HD sothat vits front contact 324 is still closed, a pick-up circuit for thedirectional stick relay 4S, including the back contact 303, the Abackcontact 3|4, and the front contact 324 of the' relaysTS, T4 and 4HDP inseries, is closed. With this directional stick .relay 4S on-ce picked upit will remain ener'- gized through one or the other of three stickcircuitsv so long as either the home-distant relay III-ID or thehome-distant repeater relay 4HDP remain in their `deenergized position;or the homedistant relay 4HD remains in its caution position. With thedirectional stick relay 4S now energized current may flow (see contact544) to the pole changer relay v4PC to in turncause current of normalpolarity to flow to the lhonnedistant relay ZHD (not shown) next in therear ofV the signal S4 only if the polar -contact 554 of thehome-distant relay 4IID isin its caution position (see similar circuitforrelay BHD in Figs. 1B and 1C of the drawings). rThe purpose andfunction of these contacts 584 and 544 will become more apparent whencorresponding ccntacts included in the energizing circuit for thepole-changer relay -5PC is considered hereinafter. It should, however,be observed that home-distant relay 3HD is held down because of theenergized'stick relay 2S (not shown but see rel-ay 8S) associated withthe signal to the rear ofsignal S4, and that this stick relay 2S will bereleased by clearing of its associated signal S2 as soon as theassociated home-distant relay returns to its right-hand clear position.

Referring now to Fig. 5A of the drawings'it will be seen that `thevehicle V! has advanced beyond the limits of the detector track circuitassociated with the West half of the siding A and is .now occupying thedetector 'track circuit associated with the east half of the passingsiding A. This produces'a very important effect upon the signalingapparatus in that it operates the signals S1 and S9 to the cautioncondition, which may for convenience be called the performance of thecaution tumble-down function. Referring to Fig. 1A it will be seen thatthe presence of the east-bound train onv the righthand half of the .maintrack -of Apassing siding A shunts and ydeenergizes -the track relay T5,thereby vcausing the .dropping of contact 525 :oi this relay T5.Since-the home-distant repeater` relay IIDP had already assumed :itsdeenergized position the dropping :of this contact 525 of relay T5causes dropping of relay SPC and pole-changing of the circuit `forhome-distant relay II-ID .and the operation of the signal S'I tothecaution position. This new circuit for relay -'IHD may be traced'through line-Wire E8 from a terminal minus back contact 495 of relay5PC, front contacts 425-5, 435-5, 445 and 455A of relays PERS-5,PBRP5-5, .T6 and TSA respectively, back contact 455 of directional stickrelay BS, front contacts 418-and48'of relays T8 :and Tl, respectively,winding of relay 1HE, through the common V-return wire C and throughback contact 4I5 of relay 5PC, vto the other terminal plus of `the samesource-of current. The operation of contacts IS7 and 20'I of relay -1HDto atheir lefthand position (relay 'IS down) will -of course cause pole`changing-of the energizing circuit for vthe horne-distant relay -QHDland roperation of this relay BHD and .signal S9 totheircaution-condition. This caution -turnble-down function thus causesall of the opposing signals 'in the single Vtrack stretch Bnext in.advance of the eastbound train VI toassume-'a caution,'ora:still morerestricted, signal aspect, as shown in lFiggl?. of the drawings.

Let us now assume that Vthe utrain `advances from the position itoccupies in Fig. :5A of the drawings to the lposition it occupies inFig. l6A ofthe drawings. Since `the rear end of the train has not lyetfully left-the passing siding A 'all 'of the signal :apparatus to therear of the train will remain in the same condition asin Fig. 5A of thedrawings. The train V I has however accepted the clear signal SB bypassing -itandhas changed tion illustrated in Fig. 1B. This dangertumble# down of signals'is"continuedthrough the medium of deenergizationof 'the' home-distant repeater relay 'II-IDP in responseto dropping'ofthe homedistant relay 'II-ID and 'by opening of front Vcon'- tacts I6'T'and 'I9'1of this relay II-IDP. It will, o'f course, 'be'und'erstoo'dthat the "directional stick relay IS still assumes its normal retractedposition and it is readily 'evident from the circuit'including backcontacts I6'7 and I9'7 of relay IHDP that this circuit 'is open'at frontcontacts I2ri Aand I4rl of the directional'stick relay 1S, as a resultof which the home-distant relay 'BHD (see Fig. 1C) is deenergized. Thisdropping of the homedistant relays 'THD and BHD and in turn theirrepeater relays 'II-IDP and SHDP will, of course, put both ofthe signalsSI- and S9 in their stop. danger or R position, as illustrated in Fig.6B of the drawings. For reasons heretofore given, itis readily seen thatdropping of the hornedistant repeater relay SHDP will. by the operationof its pole changer contacts 249 and V285, cause thehome-distant relayIIHD to be energized by current of reverse polarity and be operated toits reverse position, as a result of which the signal SII is actuated toits caution or Y condition as illustrated in Fig. 6B of the drawings.Referring to Figs. 6A and 6B it will be seen by the arrows indicatingthe conditions of the line circuits that the signal S5 energizes theline circuit extending to the signal S1 by current of .negative polarityas indicated by the minus sign at the tail end of the arrow extendingfrom signal S5 to signal S1, but that this current of negative polaritycannot flow is manifested by the Zero (0) sign near the middle of thisarrow. It will also be seen by the arrow extending from signal S'I tosignal S9 (see Fig. 6B) that the apparatus at signal location Sl applieszero potential andthat, therefore, no current .iiows in the line circuitextending to the signal S9. It is also evident that the signal S9applies current of negative polarity to the line circuit extending tothe signal SII as is manifested by the minus sign at the tail end of thearrow extending from signal S9 to signal SII, and that in this instancecurrent of negative polarity actually flows as is indicated by the minussign at the middle of this same arrow. Similarly, the arrow extendingfrom the signal SII to the signal SI3 has current of positive polarityapplied thereto a-t the signal location of the signal SII and that thiscurrent of positive polarity actually flows as is indicated by the plussign indicated near the middle of this same arrow. Attention is alsodirected to the fact that dropping of the track relay Tby entrance ofthe train VI into the single track .section B (shown in Fig. 1A) thatthe stick relay SS was picked up through back contacts 365 and 3I5 andfront contact 355 of relay SHDP before this latter relay dropped andthat two stick circuits for this relay GS were then closed.

Let us now assume that the train VI moves from the position illustratedin Fig. 6A to the position illustrated in Fig. 7A. 'Ihis change in theposition of the train VI does not change any signal indication inadvance of the train. To the rear of the train signal indications havehowever been changed since the train VI vacated the vmain track of thepassing siding A. The picking up of track relay T5 allows the current ofknegative polarity, which `is indicated by the minus sign at the tailend ofthe arrow extending from signal S6 to the signal S4, to flow. Thiscurrent flows through the winding of relay 4HD and through back contacts245 and 285 of the home-distant repeater relay SHDP (see Fig. 1A) Itshould be noted that this current iiowed through front contact 235 ofthe directional stick relay 6S so long as the train VI still shunted thetrack relay T6. This current causes the signal S4.to the rear thereof toindicate caution as is evident from the letter Y shown on the signal S4in Fig. 7A. It will also be observed that the signal S3 has been changedfrom its danger or R vindication to its clear or G indication. This iscaused by the dropping of the stick relay 2S (not shown) at the signallocation of signal S2 (shown in Fig. 27A) to the rear of the signal S4.This phase of the operation of the system will be brought out morerclearly when the position of the train, as shown in Fig. 13B, isconsidered.

As the train VI now advances from the position shown in Fig. 7A, to theposition shown in Fig. 8A, no change in the signal aspects ahead of thetrain takes place. This forward movement of the train VI however placesthe signal S8 in its kstop position because its presence -on the trackcircuit `containing track relay T8 causes deenergization of `thehome-distant relay VBHD

